Resolution‐insensitive velocity and flow rate measurement in low‐background phase‐contrast MRA

Weide, R. van der; Viergever, Max A.; Bakker, Chris J.G.

doi:10.1002/mrm.20035

Cited by 5 publications

(3 citation statements)

References 15 publications

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“…Improving phase measurements by applying noise‐filtering techniques (2–5) is generally not an applicable approach. Model‐based postprocessing schemes have been presented that use low‐resolution images with subsequently higher SNR (6, 7), but these approaches make assumptions about the type of flow present (such as laminar flow), which is only applicable in certain cases. The most general method is to increase the inherent signal of the pulse sequence itself.…”

mentioning

confidence: 99%

In‐plane velocity encoding with coherent steady‐state imaging

Grinstead¹,

Sinha²

2005

Magnetic Resonance in Med

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Standard phase-contrast flow quantification (PC-FQ) using radiofrequency (RF) spoiled steady-state (SS) incoherent gradient-echo sequences have a relatively low signal-to-noise ratio (SNR). Unspoiled SS coherent (SSC) gradient-echo sequences have a higher intrinsic SNR and are T 2 /T 1 weighted so that blood has a relatively large signal compared to other tissues. An SSC sequence that was modified to allow in-plane velocity encoding is presented. Velocity encoding was achieved by inverting the readout gradients. This offers the benefit that there is no resultant increase in repetition time (TR), which avoids increased sensitivity to off-resonance artifacts when conventional velocity-encoding methods using separate velocity-encoding gradients are extended to SSC sequences. The results of standard PC-FQ and the new method from in vitro experiments of constant and sinusoidal flow, and in vivo imaging of the carotid artery were compared. Vector field maps and paths obtained from particle-tracking calculations based on the velocity-encoded images were used to visualize the velocity data. The technique has the potential to increase the precision of PC-FQ measurements. Magn Reson Med 54:138 -145, 2005.

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mentioning

confidence: 99%

In‐plane velocity encoding with coherent steady‐state imaging

Grinstead¹,

Sinha²

2005

Magnetic Resonance in Med

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“…This widely accepted target is readily achieved in imaging the great vessels, but is a constraint for more peripheral vessels. Consequently, several authors have focused their efforts on easing this restriction (11, 26, 29–32). Similarly, vascular narrowing is clinically interesting, but often leads to flow disturbances that may corrupt the velocity estimates obtained by phase mapping (33–35).…”

Section: Methodsmentioning

confidence: 99%

Multisite trial of MR flow measurement: Phantom and protocol design

Summers

Holdsworth

Nikolov

et al. 2005

Magnetic Resonance Imaging

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Purpose: To describe a portable, easily assembled phantom with well-defined bore geometry together with a series of tests that will form the basis of a standardized quality assurance protocol in a multicenter trial of flow measurement by the MR phase mapping technique. Materials and Methods:The phantom consists of silicone polymer layers containing parallel straight and stenosed flow channels in one layer and a U-bend in a second layer, separated by hermetically sealed agarose slabs. The phantom is constructed by casting low melting-point metal in an aluminum mold precisely milled to the desired geometry, and then using the low melting-point metal core as a negative around which the silicone is allowed to set. By melting out the metal, the flow channels are established. The milled aluminum mold is reusable, ensuring faithful reproduction of the flow geometry for all phantoms thus produced. The agarose layers provide additional loading and static background signal for background correction. With the use of the described phantom, one can evaluate flow measurement accuracy and repeatability, as well as the influence of several imaging geometry factors: slice offset, in-plane position, and slice-flow obliquity. Results:The new phantom is compact and portable, and is well suited for reassembly. We were able to demonstrate its facility in a battery of tests of interest in evaluating MR flow measurements. Conclusion:The phantom is a robust standardized test object for use in a multicenter trial. Such a trial, to investigate the performance of MR flow measurement using the phantom and the tests we describe, has been initiated.

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“…When the VENC is chosen correctly, the phase shift is proportional to the velocity of the blood and can be used to determine the velocity of the blood. 11 It should also be noted that PC-MRA can be used to encode for flow both parallel and perpendicular to the imaging slice and that many postprocessing techniques use the complex data from the PC-MRA images to determine velocity and volume flow rate in the blood vessels. 11 This technique is particularly useful when flow and velocity information is needed, as in cardiac and thoracic aorta imaging.…”

Section: Noncontrast Techniquesmentioning

confidence: 99%

Theory, Technique, and Practice of Magnetic Resonance Angiography

et al. 2007

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Magnetic resonance angiography (MRA) is now a widely accepted technique used to characterize vascular pathology such as stenosis, dissection, fistula, and aneurysms. Magnetic resonance techniques are increasingly driving clinical decision making by vascular physicians. The physics behind MRA can contribute to the general understanding and interpretation of the anatomic images. We seek to provide a window into how magnetic resonance images are generated, which techniques may be employed, and the potential advantages and limitations of various techniques and to discuss the future role MRA may have for the vascular physician.

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Resolution‐insensitive velocity and flow rate measurement in low‐background phase‐contrast MRA

Cited by 5 publications

References 15 publications

In‐plane velocity encoding with coherent steady‐state imaging

In‐plane velocity encoding with coherent steady‐state imaging

Multisite trial of MR flow measurement: Phantom and protocol design

Theory, Technique, and Practice of Magnetic Resonance Angiography

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